Aneurysms result from weakening of the blood vessel, which causes the wall of the blood vessel to balloon outwardly under the hemodynamic stress of the flowing blood, thereby creating an aneurysm. Aneurysm formation and growth can have serious consequences such as pressure on the adjacent brain or other tissues and nerves and eventual rupture which can be fatal.
Given the life-threatening nature of such intracranial aneurysms, several methods of treating aneurysms have been attempted, with varying degrees of success. For example, open craniotomy is a procedure by which an aneurysm is located, and treated extravascularly. This procedure can have significant disadvantages. For example, it is an open surgery in which the surgeon must typically remove a portion of the patient's skull and violate the brain coverings, and can also traumatize brain tissue in order to reach the aneurysm.
Other known techniques used in treating aneurysms are performed endovascularly. Such techniques typically involve attempting to form a mass within the sac of the aneurysm. For instance, a microcatheter is often used to access the aneurysm, where the distal tip of the micro catheter is placed within the sac of the aneurysm, allowing for deposit of embolic material into the sac of the aneurysm. The embolic material includes, for example, detachable coils or liquid polymer. This approach, however, suffers from various disadvantages. For example, the detachable coils can exert pressure on the inside weak walls of the aneurysm, causing ruptures of the aneurysm with a potentially fatal brain hemorrhage. Additionally, coils can migrate out of the sac of the aneurysm and into the parent artery which can lead to clot formation and stroke. Another drawback is that the detachable coils can compact over time due to the space existing between the coils. Coil compaction can result in recanalization of the aneurysm caused by the continued hemodynamic forces from the blood circulation, which is particularly common in bifurcated aneurysms treated with coils.
In addition to the drawbacks associated with coils, embolic liquid migration is also a problem. For instance, when a liquid polymer is injected into the sac of the aneurysm, it can migrate out of the sac of the aneurysm, which can lead to irreversible occlusion of the parent vessel. Techniques have been developed to minimize the risk of coils and embolic liquid migration into the parent vessel, such as temporary occlusion of the parent vessel at the origin of the aneurysm using a removable balloon. However, these techniques suffer from various disadvantages also. For instance, it is sometimes undesirable to occlude the parent vessel, even temporarily. In addition, the migration prevention techniques may not prevent all embolic material migration into the parent vessel, particularly after the removing of the balloon.
Yet another technique to prevent coils migration involves depositing a permanent stent in the parent vessel across the origin of the aneurysm. This technique, however, often require premedicating the patient with strong blood thinner which can be problematic particularly in the setting of ruptured aneurysm and brain hemorrhage.
Another recent trend in endovascular technique for treating cerebral aneurysms involves permanent insertion of a tightly woven high density stent in the parent vessel across the origin of the aneurysm to divert the blood flow away from the aneurysm. This technique also suffers from the disadvantage of needing strong blood thinner, as well as potential inadvertent occlusion of some of the adjacent normal blood vessel, such as perforators. Such occlusion can lead to a devastating stroke. Moreover, the high density stent also suffers from the disadvantage that it cannot be used to treat bifurcated aneurysms.
In view of the above, there remains a need to develop new devices that effectively and safely treat cerebral aneurysms ruptured and unruptured aneurysm.